JURORS saw a small, frail-looking pensioner with a wispy white beard in the dock at the High Court in Livingston.

But as the horrific details of the World’s End case unfolded, the nine men and six women were given a horrifying glimpse into the real Angus Sinclair.

A police officer who played a major role in bringing him to justice said his quiet, polite manner hid his true nature, that of a sadistic and manipulative rapist and killer.

In reality, Sinclair was a Jekyll and Hyde character, whose cynically violent streak and obsession with sex would wreak havoc across central Scotland during the 1970s and early 80s.

Detective Superintendent Allan Jones, 52, told how he came to know Sinclair as the most dangerous criminal he had encountered in his 33-year police career.

Despite only having interviewed him once after Sinclair was charged in 2005, Mr Jones’s long involvement with the World’s End murders and the seven other murders Sinclair is suspected of having committed allowed him to see the killer’s true colours.

“When you sit opposite him, he is respectful of authority. You’re thinking, ‘How could he be the individual he is?’.

“But then there’s another part to him. Cunning, manipulating, he’s a cruel, sexually motivated individual.

“You see right from the past when he was 16 when he murdered an eight-year-old girl, then going on to trying to manipulate the situation so that it appeared that he had just come across her body and went to her aid.

Cunning, manipulating, he’s a cruel, sexually motivated individual

Detective Superintendent Allan Jones

“Right through the rest of his criminal career when you see the violence he was using toward individuals, whether it be robberies or sexual assaults and ultimately murders, was horrendous. All of that is within him. Quite why it’s there I don’t know, but it’s there. It’s present and it’s still there.

“Even though he’s 69 and he’s maybe failing in terms of health, that evil element is still there, so he’s still a danger.”

Asked how he felt interviewing Sinclair, he added: “I’ve always been able to detach myself from personal feelings toward individuals.

“There’s been no guilt or remorse, he will deny all his crimes until his dying day.

“He’s an inveterate liar, and he would see that as a weakness back then as a 16-year-old, and he’s been cunning ever since.” Many experts now believe Sinclair is Scotland’s worst serial killer, surpassing Peter Tobin, who is currently serving life in prison for the murders of three young women.

Mr Jones said that a killing spree of this magnitude had not been seen in Scotland in modern times.

He added: “There’s no other thing to compare it to, really. There have been serial killers elsewhere, in other countries. But in Scotland, no – there’s nothing else.

“Peter Tobin is clearly one of the worst killers we’ve ever seen in recent times, but Sinclair is by far the worst.”